1. Field of the Invention
The present invention relates to a light-emitting device, and in particular to a light-emitting device that has excellent heat dissipation performance.
2. The Related Arts
Light-emitting diodes (LEDs) and organic electroluminescent displays (OELDs) are two commonly used light-emitting devices at present.
The light-emitting diode comprises a semiconductor P-N junction structure to cause injections of minority charge carriers (electrons or holes) and to give of light through re-combination of the minority charge carriers. In other words, if a positive voltage is applied to a specific element of the semiconductor, the electrons and the holes, when passing through an intermediate structure between an anode and a cathode, re-combine with each other. Such a state has a energy less than that of the state where the electrons and the holes are separate from each other and thus, emission of light results due to the difference of energy at this moment.
The organic electroluminescence display comprises thin coatings of organic materials on a glass substrate, so that when an electrical currently is conduct to pass, the organic coatings get luminous.
A currently available white LED generally comprises a blue die with an external package of yellow YAG fluorescent powder so as to result in a combination of lights to generate a white light; however, the color rendering index thereof is low. Further, the base layer of an LED often comprises sapphire, which has relatively low thermal conductivity (generally less than 50 W/m.K) and this leads to poor heat dissipation of the LED, thus affecting the luminous efficiency and lifespan of the LED.
Similarly, the glass substrate of the OLED is also of thermal conductivity that is not high, similarly suffering the issue of heat dissipation.